Corbett McDonald, Rezaul Hoque, Nazmul Huda, Nicola Cherry

Objective

Arsenic concentrations in 25% of tube wells in Bangladesh exceed 50μg/L, a level known to be hazardous. Levels in individual wells vary widely. We gathered data on arsenic exposure levels and skin lesion prevalence to address the lack of knowledge about risks where the average arsenic concentrations was lower.

Methods

The nongovernmental organization Gonoshasthaya Kendra did three related studies of keratotic skin lesions since 2004: (1) an ecological prevalence survey among 13 705 women aged ⩾ 18 in a random sample of 53 villages; (2) a case-control study of 176 cases and age- and village-matched referents; and (3) a prevalence survey of the entire population of 11 670 in two additional villages. We calculated prevalence as a function of average arsenic concentrations as reported in the National Hydrochemical Survey, and measured arsenic concentrations in wells used by subjects in the case-control study.

Findings

The prevalence of skin lesions was 0.37% in people exposed to arsenic concentrations below 5μg/L, 0.63% at 6–50μg/L, and 6.84% at 81μg/L. In the case-control analysis, relative risk of skin lesions increased threefold at concentrations above 50μg/L (P < 0.05).

Conclusion

Little serious skin disease is likely to occur if the arsenic concentration in drinking water is kept below 50μg/L, but ensuring this water quality will require systematic surveillance and reliable testing of all wells, which may be impractical. More research is needed on feasible prevention of toxic effects from arsenic exposure in Bangladesh.